072  
FXHW01 KWNH 101227  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
726 AM EST SAT FEB 10 2018  
 
VALID 00Z SUN FEB 11 2018 - 00Z SUN FEB 18 2018  
 
A BROAD UPPER LOW SPINNING TO THE EAST OF THE HAWAI`IAN ISLAND  
CHAIN WILL CONTINUE ITS VERY SLOW MIGRATION TOWARD THE EAST BEFORE  
SHEARING BY EARLY NEXT WEEK. THE ACCOMPANYING SURFACE REFLECTION  
WILL FEATURE WEAKENING PRESSURE GRADIENTS THUS RESULTING IN A  
LIGHTER WIND FIELD, GENERALLY OUT OF THE NORTH-NORTHEAST BY  
SUNDAY. THERE MAY BE A BRIEF UPTICK IN THE COVERAGE OF RAIN  
SHOWERS AS A PLUME OF HIGHER PRECIPITABLE WATER PIVOTS BACK TOWARD  
THE ISLANDS.  
 
INTO EARLY NEXT WEEK, THE FOCUS SHIFTS UPSTREAM AS A BROAD UPPER  
TROUGH SWINGS EAST OF THE INTERNATIONAL DATELINE. ALONG THE  
SOUTHERN EXTENT OF THESE HEIGHT FALLS, THE GUIDANCE CONTINUES TO  
ADVERTISE A BAND OF SHORTWAVE ENERGY PEELING OFF DURING THE  
MONDAY/TUESDAY TIMEFRAME. RELATIVE TO YESTERDAY, THE BIGGEST SHIFT  
IN THE OPERATIONAL/ENSEMBLE GUIDANCE IS A MORE NORTHWARD PLACEMENT  
OF THIS UPPER LOW. INSTEAD OF APPROACHING FROM THE WEST OF  
HAWAI`I, A VAST MAJORITY OF THE ENSEMBLE MEMBERS HAVE MOVED TOWARD  
A SOLUTION WHICH PERHAPS GRAZES KAUAI AND NI`IHAU. BY WEDNESDAY,  
THERE IS QUITE A BIT OF LATERAL SPREAD WITH THE 06Z GFS/GEFS MEAN  
ON THE QUICKER SIDE WHILE THE 00Z CMC/UKMET/CMC ENSEMBLE MEAN  
PLACES WELL TO THE WEST WITH THE 00Z ECMWF/ECMWF ENSEMBLE MEAN IN  
THE MIDDLE. EXCEPT FOR THE 06Z GFS/GEFS MEAN WHICH CONTINUE TO  
ACCELERATE THIS FEATURE EASTWARD, OTHER SOLUTIONS FAVOR A GRADUAL  
EASTWARD MIGRATION WITH POTENTIAL ABSORPTION BY ANOTHER UPPER  
TROUGH TO THE NORTH. SUFFICE TO SAY, THERE IS QUITE A BIT OF MODEL  
SPREAD RELATIVE TO THE PREVIOUS DAY. GIVEN THERE IS A SLOW MOVING  
CLOSED LOW IN THE PICTURE, WOULD LIKELY STEER AWAY FROM THE  
QUICKER 06Z GFS/GEFS MEAN HERE. CONSIDERING THE SURFACE PATTERN,  
WINDS SHIFT TOWARD A MORE SOUTHEASTERLY DIRECTION AS A WARM  
ADVECTION REGIME ENSUES. DEPENDING ON THE STRENGTH OF THE UPSTREAM  
SURFACE WAVE, THERE MAY BE AN INCREASE IN WIND SPEEDS BUT  
SOLUTIONS ARE VARIABLE. OUTSIDE OF THE 00Z CMC SOLUTIONS, A  
FRONTAL PASSAGE SHOULD OCCUR SOMETIME DURING THE MIDDLE/LATTER  
PART OF THE WORK WEEK WITH THE QUICKER GFS DEPICTING THIS  
OCCURRENCE ON THE EARLIER SIDE. THE UPCOMING PATTERN SHOULD  
BOLSTER CHANCES FOR PRECIPITATION BUT IT HAS BEEN REDUCED RELATIVE  
TO YESTERDAY'S FORECAST AS THE GUIDANCE HAS CHANGED. THE DRIEST  
SOLUTION WOULD BE THE 06Z GFS/GEFS MEAN GIVEN THE MORE PROGRESSIVE  
NATURE OF THE PATTERN. THE 00Z ECMWF/CMC/UKMET ALL SUPPORT SOME  
PERIOD OF MORE ORGANIZED RAINFALL BUT UNCERTAINTY PLAGUES ANY  
ADDITIONAL DETAILS.  
 
RUBIN-OSTER  
 

 
 
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